Method and apparatus for cooling pitch



Jan. 16, 1968 E. o. OHSOL 3,3

METHOD AND APPARATUS FOR COOLING PITCH FIG.

ERNEST O. OHSOL INVENTOR.

BY Qmc AGENT Jan. 16, 1968 E. o. OHSOL 3,363,572

METHOD AND APPARATUS FOR COOLING PITCH Filed May 25, 1966 5 Sheets-Sheet 2 ERNEST O. OHSOL IN VENTOR.

AGENT Jan. 16, 1968 E. o. OHSOL 3,363,672

METHOD AND APPARATUS FOR COOLING PITCH Filed May 23, 1966 5 Sheets-Sheet 5 v F N 10 k ERNEST O. OHSOL I N VENTOR.

AGENT t United States Patent ()fliice 3,363,672 Patented Jan. 16, 1968 3,363,672 METHUI) AND APPARATUS FUR COOLING PITCH Ernest 0. Ohsol, Wilmington, DeL, assiguor to Chemical Construction Corporation, New York, N.Y., a corporation of Delaware Filed May 23, 1966, Ser. No. 552,139 13 Claims. (Cl. 165-2) The present invention relates to the cooling of pitch, and provides an improved method and apparatus for the controlled cooling of hot pitch while preventing solidification of the pitch.

Pitch is produced in a range of consistencies, depending on the source of the pitch and the processing techniques employed in its production. In general, pitch is a black or dark viscous liquid similar to tar, and the term pitch as employed in the description of the present invention will be understood to also encompass tar, in particular the viscous tars such as are produced as byproduct in the distillation of coal to manufacture coke. The coal tar which is thus produced is usually separately distilled, in order to remove lighter components leaving a residual heavy pitch. In other instances, distillation of the coal tar is not practiced or may only be provided to a limited extent, in which case a light pitch is produced. Other types of pitch or tar are produced as byproducts of the distillation of wood or the refining of petroleum. Pitch is usefully employed for a variety of purposes, such as in the treating of wood products including shingles and railroad ties to prevent rot, as well as in the paving of streets, caulking, as a component of various varnishes, etc.

One of the principal problems encountered in the processing of pitch involves the cooling of the pitch from an elevated temperature at which it is produced as a distillation residue, to the optimum temperature for subsequent utilization. Due to the viscous nature and unsatisfactory heat transfer characteristics of the pitch, the conventional liquid cooling procedure involving the provision of a cooling coil in contact with a liquid body of hot ptch, is not effective in practice, since a film of solid pitch congeals on the surface of the cooling coil and prevents further cooling of the pitch. Similar considerations ap ply to the circulation of hot pitch through a conduit which is externally cooled in a conventional manner, since in this case the pitch film on the surface of the conduit becomes solidified and plugging or clogging of the conduit rapidly takes place. Thus, such conventional direct contact and indirect cooling apparatus of the prior art as described in US. Patents Nos. 3,132,190; 2,611,153; 2,-

566,929; 2,545,028; 2,310,121; 2,086,222; 1,943,855 and 610,812 are ineffective for the cooling of hot pitch.

In the present invention, a method and apparatus for the cooling of hot pitch is provided in which a plurality of parallel passages are heated to a temperature above the solidification point of pitch, which is generally above about 110 C. The stream of hot pitch which is to be cooled is then passed through the heated passages, and an ambient air stream is passed external to the passages. In most instances and for optimum results, the ambient a r stream is passed parallel to the passages so that the air stream flows co-currently With the hot pitch inside the passages, and co-current cooling of the hot pitch is attained with concomitant heating of the air stream. A

stream of cooled pitch is removed from the passages, and

the feed rate of the hot pitch is regulated to produce the cooled pitch stream at a substantially constant temperature level above the temperature at which solidification occurs. The initial heating of the passages is preferably attained by passing heated air external to the passages, and the cooled pitch may 'be recycled to a body of hot pitch from which the hot pitch stream is withdrawn, so that the entire body of hot pitch is effectively cooled without solidification. In order to improve heat transfer from the hot pitch to the ambient air, the passages may be provided with external fins.

The present invention provides significant advantages in that a stream of hot liquid pitch is effectively cooled to a lower temperature level without soldification or the formation of a solid pitch film. The procedure does not entail a highly complex method procedure or apparatus assemblage, however close temperature control is attained and uniform cooling of the hot pitch is provided Without localized solidification as is encountered in the prior art.

It is an object of the present invention to provide an improved method and apparatus for the cooling of hot pitch.

Another object is to cool a stream of hot pitch while avoiding solidification of the pitch.

A further object is to cool a stream of hot pitch employing ambient air as an effective cooling agent.

An additional object is to cool a stream of hot pitch while preventing solidification by passing the hot pitch through a plurality of parallel passages while passing an ambient air stream external to and parallel with the passages, so that the air stream flows co-currently with the hot pitch stream and is heated while: cooling the hot pitch to a substantially constant lower temperature level above the temperature at which solidification occurs.

These and other objects and advantages of the present invention will become evident from the description which follows. Referring to the figures,

FIGURE 1 provides a flowsheet of the overall procedure of the present invention,

FIGURE 2 is a sectional elevation view of a portion of FIGURE 1, taken on section 2-2, and

FIGURE 3 is an overall isometric view of the apparatus of the invention.

Referring now to FIGURE 1, ambient air stream 1 is passed by blower 2 as stream 3 into the elongated horizontally oriented container 4, and flows parallel with the spaced apart horizontal conduits 5 which are provided with external fins 6 for improved heat transfer. At startup of the system, when the conduits 5 are at a relatively low temperature, a fluid hydrocarbon stream 7 which may consist of natural gas, fuel oil or other combustible fluid hydrocarbon is passed through valve 8 and passes via stream 9 to burner 10. The fluid hydrocarbon is burned in the air stream, and raises the temperature of the air stream flowing through container 4 so that the hot air serves to heat the conduits 5 to a temperature above about C., thus preventing solidification of the hot pitch within the conduits 5 when the pitch is. initially passed through the conduits 5. The air stream 11 discharged from container 4 passes through temperature measurement and control device 12, which consists of a suitable control instrument usually of the pneumatic or electronic type. The air stream 13 passing from unit 12 is discharged to atmosphere. When the temperature of the conduits 5 reaches a desired level, measured as a function of outlet air temperature by control device 12, the control loop 14 closes the valve 8 and terminates the flow of fluid hydrocarbon to burner 10. Alternatively, the temperature of the conduits 5 during the heating period may be measured directly by attaching thermocouples to one or several of the conduits 5, in which case the thermocouples would extend to a control device serving to regulate valve 8 and unit 12 would be omitted- After the temperature of conduits 5 has reached a desired elevated level and the combustion of fluid hydrocarbon by burner 10 has ceased, the operation of blower 2 and the flow of air through container 4 are continued,

3 3 so as to pass ambient air external to and co-currently parallel with conduits 5. The hot pitch which is to be cooled is then passed through conduits 5. The hot pitch stream passes via circulating pump 16 and is discharged as stream 17, and flows through control valve 13 and is distributed to conduits 5 as stream 19, The hot pitch flowing through conduits 5 is thus cooled to a suitable lower temperature, with heat transfer to the co-currently flowing ambient air being aided by the fins 6. The warmed air is discharged via streams I1 and 13, while the cooled pitch is removed from conduits 5 via stream Ztl and is passed through temperature measuring and control device 21, which may be similar to unit 12. Unit 21 serves to control the temperature of the cooled pitch by transmitting a control signal via loop 22 to valve 18, thus regulating the flow of hot pitch to conduits 5 so as to produce the cooled pitch stream at a substantially constant temperature level above the temperature at which solidification occurs. The final cooled pitch stream 23 discharged from unit 21 is passed to product utilization. In instances where it is desired to cool a large body of hot pitch, stream 15 is withdrawn from the body of pitch, not shown, and stream 23 is recycled to the body of pitch, thus cooling the entire body of pitch to a desired lower temperature.

FIGURE 2 is a sectional elevation view of FIGURE 1, taken on section 2-2, and shows a typical arrangement of the longitudinal cooling fins 6 external to the conduits 5.

FIGURE 3 provides an isometric view of the apparatus of the invention, and illustrates the parallel arrangement of the conduits 5. The cooling fins 6 have been omitted from FIGURE 3 in the interest of clarity, and also since the cooling fins 6 may be omitted in suitable instances. The incoming hot pitch is passed by the feed manifold 24 to the distributing manifolds 25, which in turn distribute the hot pitch to conduits 5. The cooled pitch is collected by manifolds 26 and passed to the discharge manifold 27.

Various alternatives within the scope or the present invention will occur to those skilled in the art. Thus, the co-current parallel flow of the cooling ambient air and the hot pitch serves to produce optimum results in terms of regulated cooling without solidification, however, in suitable instances countercurrent or even transverse flow of the air may be adopted in practice.

While the configuration of the container 4 has been illustrated and described as rectangular and horizontally extended, the container 4 may also be circular in which case the conduits 5 may be oriented in linear radial banks or in circular concentric banks. The container 4 and conduits 5 may also be vertically oriented in suitable instances, such as when processing a very viscous fluid pitch, with downward flow of the pitch. In this case, the blower 5 would be usually oriented so as to blow the cooling air upwards, so as to achieve the assistance of natural draft in the circulation of air,

An example of an industrial application of the invention will now be described.

Example A facility was provided for the cooling of 1000 kg./ hr. of hot pitch from an initial temperature of 250 C. to a final temperature of 130 C. The pitch had a melting point of 120 C., and continuous flow was maintained through the cooler without solidification or plugging. The air inlet temperature during the initial heating of the conduits 5 was 130 C. Thereafter, during the normal pitch cooling operation of the facility, the ambient air inlet temperature was 30 C. and the heated air was discharged at C. Inlet ambient air flow was 5950 cubic meters per hour, and 44 square meters of total heat exchange surface was provided.

I claim:

I. A method for cooling hot pitch without solidification which comprises heating a plurality of parallel passages to a temperature above about 110 C., passing a stream of hot pitch through said heated passages, passing an ambient air stream external to said passages, whereby said air stream is heated and thereby cools said hot pitch stream, removing a stream of cooled pitch from said passages, and regulating the feed rate of said hot pitch stream to produce said cooled pitch stream at a substantially constant temperature level above the temperature at which solidification occurs.

2. A method for cooling hot pitch without solidification which comprises heating a plurality of parallel passages to a temperature above about C., passing a stream of hot pitch through said heated passages, passing an ambient air stream external to and parallel with said passages, whereby said air stream flows co-currently with said hot pitch stream, and is heated and thereby cools said hot pitch stream, removing a stream of cooled pitch from said passages, and regulating the feed rate of said hot pitch stream to produce said cooled pitch stream at a substantially constant temperature level above the temperature at which solidification occurs.

3. The method of claim 2, in which said plurality of passages are horizontal.

4. The method of claim 2, in which said plurality of passages are provided with external fins, to produce improved heat transfer from said hot pitch stream to said air stream.

5. The method of claim 2, in which said plurality of passages are heated by passing heated air external to said passages.

6. A method for cooling hot pitch without solidification which comprises passing a stream of air external to and parallel with a plurality of parallel passages, heating said air stream until said passages are heated to a temperature above about 110 C., thereafter terminating the heating of said air stream whereby said air stream flows external to said passages at ambient temperature, passing a stream of hot pitch through said heated passages, whereby said hot pitch stream flows co-currently with said ambient air stream and is cooled by indirect heat exchange with said ambient air stream, removing a stream of cooled pitch from said passages, and regulating the feed rate of said hot pitch stream to produce said cooled pitch stream at a substantially constant temperature level above the temperature at which solidification occurs.

7. The method of claim 6, in which said plurality of passages are horizontal.

8. The method of claim 6, in which said plurality of passages are provided with external fins, to produce improved heat transfer from said hot pitch stream to said air stream.

9. The method of claim 6, in which said hot pitch stream is withdrawn from a body of hot pitch, and said cooled pitch stream is added to said body of hot pitch, whereby said body of hot pitch is cooled to a lower temperature level,

10. The method of claim 6, in which said air stream is heated by burning a fluid hydrocarbon in said air stream.

11. An apparatus for cooling pitch without solidification which comprises an elongated horizontally oriented container, a plurality of spaced apart horizontal conduits within said container, said conduits being aligned parallel to the horizontal axis of said container, an air blower, said blower being disposed adjacent to one end of said contamer so as to pass a stream of air through said container external to and parallel with said conduits, a fluid hydrocarbon burner, said burner being disposed adjacent to the outlet of said blower, means to pass a fluid hydrocarbon to said burner whereby said air stream is heated by combustion of said fluid hydrocarbon, means to terminate the flow of said fluid hydrocarbon to said burner when the temperature of said conduits is elevated to a level above the solidification point of pitch, means to pass a stream of hot pitch through said conduits after the flow of said fiuid hydrocarbon is terminated, whereby said hot pitch stream is cooled, means to remove a cooled pitch stream from said conduits, and means to regulate the feed rate of said hot pitch stream to produce said cooled pitch stream at a substantially constant temperature level above the temperature at which solidification occurs.

12. The apparatus of claim 11, in which said conduits are provided with external fins.

13. The apparatus of claim 11, in which said means to pass hot pitch through said conduits is connected with the ends of said conduits adjacent to said air blower, whereby said hot pitch stream flows co-currently with said air stream.

No references cited.

ROBERT A. OLEARY, Primary Examiner. C. SUKALO, Assistant Examiner. 

1. A METHOD FOR COOLING HOT PITCH WITHOUT SOLIDIFICATION WHICH COMPRISES HEATING A PLURALITY OF PARALLEL PASSAGES TO A TEMPERATURE ABOVE ABOUT 110*C., PASSING A STREAM OF HOT PITCH THROUGH SAID HEATED PASSAGES, PASSING AN AMBIENT AIR STREAM EXTERNAL TO SAID PASSAGES, WHEREBY SAID AIR STREAM IS HEATED AND THEREBY COOLS SAID HOT PITCH STREAM, REMOVING A STREAM OF COOLED PITCH FROM SAID PAS- 